function f_plot_CM(CM)
% maxc = max(max(CM));
maxc =20;
for ix = 1:length(CM)
    for iy = length(CM):-1:1
        s = area([ix-1 ix],[iy iy],iy-1);hold on;
        set(s,'facecolor',[1 1 1]-CM(ix,iy)./maxc.*[1 1 1]);
    end
end
hold on;
plot([0 length(CM)],[0 length(CM)],'b');
axis([0 length(CM) 0 length(CM)]);